summaryrefslogtreecommitdiffstats
path: root/src/payload.c
blob: 23afa2f21709983a7c2f38508f46d5ce76125a39 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
/*
 * Payload expression and related functions.
 *
 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <net/if_arp.h>
#include <arpa/inet.h>
#include <linux/netfilter.h>

#include <rule.h>
#include <expression.h>
#include <statement.h>
#include <payload.h>
#include <gmputil.h>
#include <utils.h>

static void payload_expr_print(const struct expr *expr)
{
	const struct proto_desc *desc;
	const struct proto_hdr_template *tmpl;

	desc = expr->payload.desc;
	tmpl = expr->payload.tmpl;
	if (desc != NULL && tmpl != NULL)
		printf("%s %s", desc->name, tmpl->token);
	else
		printf("payload @%s,%u,%u",
		       proto_base_tokens[expr->payload.base],
		       expr->payload.offset, expr->len);
}

static bool payload_expr_cmp(const struct expr *e1, const struct expr *e2)
{
	return e1->payload.desc   == e2->payload.desc &&
	       e1->payload.tmpl   == e2->payload.tmpl &&
	       e1->payload.base   == e2->payload.base &&
	       e1->payload.offset == e2->payload.offset;
}

static void payload_expr_clone(struct expr *new, const struct expr *expr)
{
	new->payload.desc   = expr->payload.desc;
	new->payload.tmpl   = expr->payload.tmpl;
	new->payload.base   = expr->payload.base;
	new->payload.offset = expr->payload.offset;
}

/**
 * payload_expr_pctx_update - update protocol context based on payload match
 *
 * @ctx:	protocol context
 * @expr:	relational payload expression
 *
 * Update protocol context for relational payload expressions.
 */
static void payload_expr_pctx_update(struct proto_ctx *ctx,
				     const struct expr *expr)
{
	const struct expr *left = expr->left, *right = expr->right;
	const struct proto_desc *base, *desc;
	unsigned int proto = 0;

	if (!(left->flags & EXPR_F_PROTOCOL))
		return;

	assert(expr->op == OP_EQ);

	/* Export the data in the correct byte order */
	assert(right->len / BITS_PER_BYTE <= sizeof(proto));
	mpz_export_data(constant_data_ptr(proto, right->len), right->value,
			right->byteorder, right->len / BITS_PER_BYTE);

	base = ctx->protocol[left->payload.base].desc;
	desc = proto_find_upper(base, proto);

	assert(left->payload.base + 1 <= PROTO_BASE_MAX);
	proto_ctx_update(ctx, left->payload.base + 1, &expr->location, desc);
}

static const struct expr_ops payload_expr_ops = {
	.type		= EXPR_PAYLOAD,
	.name		= "payload",
	.print		= payload_expr_print,
	.cmp		= payload_expr_cmp,
	.clone		= payload_expr_clone,
	.pctx_update	= payload_expr_pctx_update,
};

struct expr *payload_expr_alloc(const struct location *loc,
				const struct proto_desc *desc,
				unsigned int type)
{
	const struct proto_hdr_template *tmpl;
	enum proto_bases base;
	struct expr *expr;
	unsigned int flags = 0;

	if (desc != NULL) {
		tmpl = &desc->templates[type];
		base = desc->base;
		if (type == desc->protocol_key)
			flags = EXPR_F_PROTOCOL;
	} else {
		tmpl = &proto_unknown_template;
		base = PROTO_BASE_INVALID;
		desc = &proto_unknown;
	}

	expr = expr_alloc(loc, &payload_expr_ops, tmpl->dtype,
			  tmpl->byteorder, tmpl->len);
	expr->flags |= flags;

	expr->payload.desc   = desc;
	expr->payload.tmpl   = tmpl;
	expr->payload.base   = base;
	expr->payload.offset = tmpl->offset;

	return expr;
}

void payload_init_raw(struct expr *expr, enum proto_bases base,
		      unsigned int offset, unsigned int len)
{
	expr->payload.base	= base;
	expr->payload.offset	= offset;
	expr->len		= len;
}

/**
 * payload_gen_dependency - generate match expression on payload dependency
 *
 * @ctx:	evaluation context
 * @expr:	payload expression
 * @res:	dependency expression
 *
 * Generate matches on protocol dependencies. There are two different kinds
 * of dependencies:
 *
 * - A payload expression for a base above the hook base requires a match
 *   on the protocol value in the lower layer header.
 *
 * - A payload expression for a base below the hook base is invalid in the
 *   output path since the lower layer header does not exist when the packet
 *   is classified. In the input path a payload expressions for a base exactly
 *   one below the hook base is valid. In this case a match on the device type
 *   is required to verify that we're dealing with the expected protocol.
 *
 *   Note: since it is unknown to userspace which hooks a chain is called from,
 *   it is not explicitly verified. The NFT_META_IIFTYPE match will only match
 *   in the input path though.
 */
int payload_gen_dependency(struct eval_ctx *ctx, const struct expr *expr,
			   struct stmt **res)
{
	const struct hook_proto_desc *h = &hook_proto_desc[ctx->pctx.family];
	const struct proto_desc *desc;
	const struct proto_hdr_template *tmpl;
	struct expr *dep, *left, *right;
	struct stmt *stmt;
	int protocol;
	uint16_t type;

	if (expr->payload.base < h->base) {
		if (expr->payload.base < h->base - 1)
			return expr_error(ctx->msgs, expr,
					  "payload base is invalid for this "
					  "family");

		if (proto_dev_type(expr->payload.desc, &type) < 0)
			return expr_error(ctx->msgs, expr,
					  "protocol specification is invalid "
					  "for this family");

		left = meta_expr_alloc(&expr->location, NFT_META_IIFTYPE);
		right = constant_expr_alloc(&expr->location, &arphrd_type,
					    BYTEORDER_HOST_ENDIAN,
					    2 * BITS_PER_BYTE, &type);

		dep = relational_expr_alloc(&expr->location, OP_EQ, left, right);
		stmt = expr_stmt_alloc(&dep->location, dep);
		if (stmt_evaluate(ctx, stmt) < 0) {
			return expr_error(ctx->msgs, expr,
					  "dependency statement is invalid");
		}
		*res = stmt;
		return 0;
	}

	desc = ctx->pctx.protocol[expr->payload.base - 1].desc;
	/* Special case for mixed IPv4/IPv6 and bridge tables */
	if (desc == NULL) {
		switch (ctx->pctx.family) {
		case NFPROTO_INET:
			switch (expr->payload.base) {
			case PROTO_BASE_LL_HDR:
				desc = &proto_inet;
				break;
			case PROTO_BASE_TRANSPORT_HDR:
				desc = &proto_inet_service;
				break;
			default:
				break;
			}
			break;
		case NFPROTO_BRIDGE:
		case NFPROTO_NETDEV:
			switch (expr->payload.base) {
			case PROTO_BASE_LL_HDR:
				desc = &proto_eth;
				break;
			case PROTO_BASE_TRANSPORT_HDR:
				desc = &proto_inet_service;
				break;
			default:
				break;
			}
			break;
		}
	}

	if (desc == NULL)
		return expr_error(ctx->msgs, expr,
				  "ambiguous payload specification: "
				  "no %s protocol specified",
				  proto_base_names[expr->payload.base - 1]);

	protocol = proto_find_num(desc, expr->payload.desc);
	if (protocol < 0)
		return expr_error(ctx->msgs, expr,
				  "conflicting protocols specified: %s vs. %s",
				  desc->name, expr->payload.desc->name);

	tmpl = &desc->templates[desc->protocol_key];
	if (tmpl->meta_key)
		left = meta_expr_alloc(&expr->location, tmpl->meta_key);
	else
		left = payload_expr_alloc(&expr->location, desc, desc->protocol_key);

	right = constant_expr_alloc(&expr->location, tmpl->dtype,
				    tmpl->dtype->byteorder, tmpl->len,
				    constant_data_ptr(protocol, tmpl->len));

	dep = relational_expr_alloc(&expr->location, OP_EQ, left, right);
	stmt = expr_stmt_alloc(&dep->location, dep);
	if (stmt_evaluate(ctx, stmt) < 0) {
		return expr_error(ctx->msgs, expr,
					  "dependency statement is invalid");
	}
	left->ops->pctx_update(&ctx->pctx, dep);
	*res = stmt;
	return 0;
}

/**
 * payload_expr_complete - fill in type information of a raw payload expr
 *
 * @expr:	the payload expression
 * @ctx:	protocol context
 *
 * Complete the type of a raw payload expression based on the context. If
 * insufficient information is available the expression remains unchanged.
 */
void payload_expr_complete(struct expr *expr, const struct proto_ctx *ctx)
{
	const struct proto_desc *desc;
	const struct proto_hdr_template *tmpl;
	unsigned int i;

	assert(expr->ops->type == EXPR_PAYLOAD);

	desc = ctx->protocol[expr->payload.base].desc;
	if (desc == NULL)
		return;
	assert(desc->base == expr->payload.base);

	for (i = 0; i < array_size(desc->templates); i++) {
		tmpl = &desc->templates[i];
		if (tmpl->offset != expr->payload.offset ||
		    tmpl->len    != expr->len)
			continue;
		expr->dtype	   = tmpl->dtype;
		expr->payload.desc = desc;
		expr->payload.tmpl = tmpl;
		return;
	}
}

static unsigned int mask_to_offset(const struct expr *mask)
{
	return mask ? mpz_scan1(mask->value, 0) : 0;
}

static unsigned int mask_length(const struct expr *mask)
{
	unsigned long off;

        off = mask_to_offset(mask);

	return mpz_scan0(mask->value, off + 1);
}

/**
 * payload_expr_trim - trim payload expression according to mask
 *
 * @expr:	the payload expression
 * @mask:	mask to use when searching templates
 * @ctx:	protocol context
 *
 * Walk the template list and determine if a match can be found without
 * using the provided mask.
 *
 * If the mask has to be used, trim the mask length accordingly
 * and return true to let the caller know that the mask is a dependency.
 */
bool payload_expr_trim(struct expr *expr, struct expr *mask,
		       const struct proto_ctx *ctx)
{
	unsigned int payload_offset = expr->payload.offset + mask_to_offset(mask);
	unsigned int mask_len = mask_length(mask);
	const struct proto_hdr_template *tmpl;
	unsigned int payload_len = expr->len;
	const struct proto_desc *desc;
	unsigned int i, matched_len = mask_to_offset(mask);

	assert(expr->ops->type == EXPR_PAYLOAD);

	desc = ctx->protocol[expr->payload.base].desc;
	if (desc == NULL)
		return false;

	assert(desc->base == expr->payload.base);

	if (ctx->protocol[expr->payload.base].offset) {
		assert(payload_offset >= ctx->protocol[expr->payload.base].offset);
		payload_offset -= ctx->protocol[expr->payload.base].offset;
	}

	for (i = 1; i < array_size(desc->templates); i++) {
		tmpl = &desc->templates[i];
		if (tmpl->offset != payload_offset)
			continue;

		if (tmpl->len > payload_len)
			return false;

		payload_len -= tmpl->len;
		matched_len += tmpl->len;
		payload_offset += tmpl->len;
		if (payload_len == 0)
			return false;

		if (matched_len == mask_len) {
			assert(mask->len >= mask_len);
			mask->len = mask_len;
			return true;
		}
	}

	return false;
}

/**
 * payload_expr_expand - expand raw merged adjacent payload expressions into its
 * 			 original components
 *
 * @list:	list to append expanded payload expressions to
 * @expr:	the payload expression to expand
 * @mask:	optional/implicit mask to use when searching templates
 * @ctx:	protocol context
 *
 * Expand a merged adjacent payload expression into its original components
 * by splitting elements off the beginning matching a payload template.
 *
 * Note: this requires all payload templates to be specified in ascending
 * 	 offset order.
 */
void payload_expr_expand(struct list_head *list, struct expr *expr,
			 struct expr *mask, const struct proto_ctx *ctx)
{
	unsigned int off = mask_to_offset(mask);
	const struct proto_hdr_template *tmpl;
	const struct proto_desc *desc;
	struct expr *new;
	unsigned int i;

	assert(expr->ops->type == EXPR_PAYLOAD);
	assert(!mask || mask->len != 0);

	desc = ctx->protocol[expr->payload.base].desc;
	if (desc == NULL)
		goto raw;
	assert(desc->base == expr->payload.base);

	for (i = 1; i < array_size(desc->templates); i++) {
		tmpl = &desc->templates[i];
		if (tmpl->offset != expr->payload.offset)
			continue;

		if (tmpl->len <= expr->len) {
			new = payload_expr_alloc(&expr->location, desc, i);
			list_add_tail(&new->list, list);
			expr->len	     -= tmpl->len;
			expr->payload.offset += tmpl->len;
			if (expr->len == off)
				return;
		} else
			break;
	}
raw:
	new = payload_expr_alloc(&expr->location, NULL, 0);
	payload_init_raw(new, expr->payload.base, expr->payload.offset,
			 expr->len);
	list_add_tail(&new->list, list);
}

/**
 * payload_is_adjacent - return whether two payload expressions refer to
 * 			 adjacent header locations
 *
 * @e1:		first payload expression
 * @e2:		second payload expression
 */
bool payload_is_adjacent(const struct expr *e1, const struct expr *e2)
{
	if (e1->payload.offset % BITS_PER_BYTE || e1->len % BITS_PER_BYTE ||
	    e2->payload.offset % BITS_PER_BYTE || e2->len % BITS_PER_BYTE)
		return false;

	if (e1->payload.base		 == e2->payload.base &&
	    e1->payload.offset + e1->len == e2->payload.offset)
		return true;
	return false;
}

/**
 * payload_expr_join - join two adjacent payload expressions
 *
 * @e1:		first payload expression
 * @e2:		second payload expression
 */
struct expr *payload_expr_join(const struct expr *e1, const struct expr *e2)
{
	struct expr *expr;

	assert(payload_is_adjacent(e1, e2));

	expr = payload_expr_alloc(&internal_location, NULL, 0);
	expr->payload.base   = e1->payload.base;
	expr->payload.offset = e1->payload.offset;
	expr->len	     = e1->len + e2->len;
	return expr;
}